Scintillator panel and radiation image sensor

ABSTRACT

The surfaces of an amorphous carbon substrate  10  of a scintillator panel  1  have undergone sandblasting, and an Al film  12  serving as a reflecting film is formed on one surface. A columnar scintillator  14  for converting incident radiation into visible light is formed on the surface of the Al film  12.

RELATED APPLICATION

This application is a Continuation patent application of U.S.application Ser. No. 09/560,911 filed on Apr. 28, 2000, now U.S. Pat.No. 6,531,225, which is a Continuation-in-Part application ofInternational Application No. PCT/JP99/01911 filed on Apr. 9, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scintillator panel and radiationimage sensor used for medical X-ray photography and the like.

2. Related Background Art

Conventionally, X-ray photosensitive films have been used for medicaland industrial X-ray photography. However, radiation imaging systemsusing radiation detectors have come into widespread use owing toadvantages in convenience and retention of photographic results. In sucha radiation imaging system, pixel data based on 2D radiation is acquiredas an electrical signal by the radiation detector, and the signal isprocessed by the processor and displayed on the monitor.

As a conventional, typical radiation detector, a radiation detectorhaving a structure in which an image sensing element is stuck to ascintillator panel having a scintillator formed on a substrate made ofaluminum, glass, molten quartz, or the like is available. In thisradiation detector, the scintillator converts radiations incident fromthe substrate side into light, and the image sensing element detects thelight (see Japanese Patent Publication No. 7-21560).

A radiation detector for medical purposes, especially for dentalexamination, uses low-energy X-rays. If, therefore, an aluminumsubstrate is used, quite a few X-ray components are absorbed by thesubstrate. In a radiation detector using low-energy X-rays, therefore,the substrate of the scintillator panel is required to have highradiation transmittance.

It is an object of the present invention to provide a scintillator panelwhich increases the optical output by using a substrate having highradiation transmittance for the scintillator panel, and a radiationimage sensor using the scintillator panel.

SUMMARY OF THE INVENTION

A scintillator panel of the present invention is characterized bycomprising a substrate made of carbon as a major constituent, areflecting film formed on said substrate, a scintillator deposited onsaid reflecting film, a protective film covering said substrate and saidscintillator.

According to this scintillator panel, since the substrate made of carbonas a major constituent has high radiation transmittance, the amount ofradiation absorbed by the substrate can be decreased, and the amount ofradiation reaching the scintillator can be increased.

A radiation image sensor according to the present invention ischaracterized by having an image sensing element placed to oppose thescintillator of the scintillator panel comprising a substrate made ofcarbon as a major constituent, a scintillator deposited on thesubstrate, and a protective film covering the scintillator.

According to this radiation image sensor, since the scintillator panelhas the substrate made of carbon as a major constituent having highradiation transmittance, the amount of light reaching the image sensingelement can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a scintillator panel according to thefirst embodiment;

FIG. 2 is a sectional view of a radiation image sensor according to thefirst embodiment;

FIG. 3A is a view showing the step in manufacturing the scintillatorpanel according to the first embodiment;

FIG. 3B is a view showing the step in manufacturing the scintillatorpanel according to the first embodiment;

FIG. 3C is a view showing the step in manufacturing the scintillatorpanel according to the first embodiment;

FIG. 3D is a view showing the step in manufacturing the scintillatorpanel according to the first embodiment;

FIG. 4 is a sectional view of a scintillator panel according to thesecond embodiment;

FIG. 5 is a sectional view of a radiation image sensor according to thesecond embodiment;

FIG. 6 is a sectional view of a scintillator panel according to thethird embodiment;

FIG. 7 is a sectional view of a radiation image sensor according to thethird embodiment;

FIG. 8 is a sectional view of a scintillator panel according to thefourth embodiment;

FIG. 9 is a sectional view of a radiation image sensor according to thefourth embodiment; and

FIG. 10 is a view showing outputs from the radiation image sensorsaccording to the first to fourth embodiments in comparison with outputsfrom the conventional radiation image sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present invention will be described belowwith reference to FIGS. 1, 2, and 3A to 3D. FIG. 1 is a sectional viewof a scintillator panel 1. FIG. 2 is a sectional view of a radiationimage sensor 2.

As shown in FIG. 1, the surfaces of an amorphous carbon (a-C) (glassycarbon or glass-like carbon) substrate 10 have undergone sandblasting,and an Al film 12 serving as a reflecting film is formed on one surface.A columnar scintillator 14 for converting incident radiation intovisible light is formed on the surface of the Al film 12. Note thatTl-doped CsI is used for the scintillator 14. The scintillator 14 iscovered with a polyparaxylylene film 16, together with the substrate 10.

As shown in FIG. 2, the radiation image sensor 2 has a structure inwhich an image sensing element 18 is stuck to the distal end side of thescintillator 14.

The steps in manufacturing the scintillator panel 1 will be describednext with reference to FIGS. 3A to 3D. Sandblasting is performed on thesurfaces of the rectangular or circular a-C substrate 10 (thickness: 1mm) by using glass beads (#800). Fine projections/recesses are formed onthe surfaces of the substrate 10 by this sandblasting (see FIG. 3A).

The Al film 12 serving as a reflecting film is then formed on onesurface of the substrate 10 to a thickness of 100 nm by vacuum vapordeposition (see FIG. 3B). A Tl-doped columnar CsI crystal is grown onthe surface of the Al film 12 by vapor deposition to form thescintillator 14 having a thickness of 250 μm (see FIG. 3C).

CsI used to form this scintillator 14 has high hygroscopicity, and henceabsorbs water vapor from the air and deliquesces if it is kept exposedto the air. In order to prevent this, the polyparaxylylene film 16 isformed by the CVD method. More specifically, the substrate 10 on whichthe scintillator 14 is formed is placed in a CVD apparatus, and thepolyparaxylylene film 16 is formed to a thickness of 10 μm. With thisprocess, the polyparaxylylene film 16 is formed on the entire surfacesof the scintillator 14 and substrate 10 (see FIG. 3D). Since thepolyparaxylylene film 16 is formed on the surfaces of the substrate 10,the moisture-proof characteristics of the scintillator 14 can beimproved. In addition, since the polyparaxylylene film 16 is formed onthe entire surfaces of the substrate 10, the moisture-proofcharacteristics of the scintillator 14 can be further improved.

Note that the formation of the fine projections/recesses on the surfacesof the substrate 10 by sandblasting can improve the adhesioncharacteristics between the polyparaxylylene film 16 and the substrate10, thus preventing peeling of the polyparaxylylene film 16.

The radiation image sensor 2 is manufactured by sticking the imagesensing element (CCD) 18 to the distal end portion side of thescintillator 14 of the completed scintillator panel 1 such that thelight-receiving portion opposes the distal end portion side (see FIG.2).

According to the radiation image sensor 2 of this embodiment, radiationincident from the substrate 10 side is converted into light by thescintillator 14 and detected by the image sensing element 18. In thiscase, since a-C substrate 10 has high radiation transmittance, theamount of radiation absorbed by the substrate 10 can be reduced. Hence,the amount of radiation reaching the scintillator 14 can be increased.In addition, since the Al film 12 as a reflecting film is formed, lightincident on the light-receiving portion of the image sensing element 18can be increased. This makes it possible to sharpen the image detectedby the radiation image sensor.

FIG. 10 shows outputs from the radiation image sensor 2 which areobtained when the radiation image sensor 2 detects the X-rays generatedby applying 40 kV, 50 kV, and 60 kV as tube voltages to the half-waverectifying x-ray tube, in comparison with outputs from the conventionalradiation image sensor. More specifically, if the output obtained whenthe conventional radiation image sensor detects the X-ray generated byapplying 40 kv as a tube voltage to the half-wave rectifying X-ray tubeis assumed to be 100%, the output obtained when the X-ray is detected bythe radiation image sensor 2 is 260%. If the output obtained when theconventional radiation image sensor detects the X-ray generated byapplying 50 kV as a tube voltage to the half-wave rectifying X-ray tubeis assumed to be 100%, the output obtained when the X-ray is detected bythe radiation image sensor 2 is 230%. If the output obtained when theconventional radiation image sensor detects the X-ray generated byapplying 60 kV as a tube voltage to the half-wave rectifying X-ray tubeis assumed to be 100%, the output obtained when the x-ray is detected bythe radiation image sensor 2 is 220%.

The second embodiment of the present invention will be described next.Note that the same reference numerals denoting the parts of thescintillator panel 1 and radiation image sensor 2 as in the firstembodiment denote the same parts in the second embodiment.

FIG. 4 is a sectional view of a scintillator panel 3. FIG. 5 is asectional view of a radiation image sensor 4. As shown in FIG. 4, thesurfaces of a-C substrate 10 of the scintillator panel 3 have undergonesandblasting, and an Al film 12 serving as a reflecting film is formedon one surface. As a low-refractive-index member, an LiF film (thintransparent film) 22 having a refractive index (refractive index=1.3)lower than that of a scintillator 14 is formed on the Al film 12. Thecolumnar scintillator 14 for converting incident radiation into visiblelight is formed on the surface of the LiF film 22. Note that Tl-dopedCsI (refractive index=1.8) is used for the scintillator 14. Thescintillator 14 is covered with a polyparaxylylene film 16, togetherwith the substrate 10.

As shown in FIG. 5, the radiation image sensor 4 has a structure inwhich an image sensing element 18 is stuck to the scintillator 14 sideof the scintillator panel 3.

The steps in manufacturing the scintillator panel 3 will be describednext. First of all, sandblasting is performed on the surfaces of therectangular or circular a-C substrate 10 (thickness: 1 mm) by usingglass beads (#800) thereby forming fine projections/recesses on thesurfaces of the substrate 10.

The Al film 12 serving as a reflecting film is then formed on onesurface of the substrate 10 to a thickness of 100 nm by vacuum vapordeposition, and the LiF film 22 as a low-refractive-index member isformed on the Al film 12 to a thickness of 100 nm by vacuum vapordeposition. A Tl-doped columnar CsI crystal is grown on the surface ofthe LiF film 22 by vapor deposition to form the scintillator 14 having athickness of 250 μm. The polyparaxylylene film 16 is formed to athickness of 10 μm by the CVD method. With this process, thepolyparaxylylene film 16 is formed on the entire surfaces of thescintillator 14 and substrate 10. Since the polyparaxylylene film 16 isformed on the surfaces of the substrate 10, the moisture-proofcharacteristics of the scintillator 14 can be improved. In addition,since the polyparaxylylene film 16 is formed on the entire surfaces ofthe substrate 10, the moisture-proof characteristics of the scintillator14 can be further improved.

The radiation image sensor 4 is manufactured by sticking the imagesensing element (CCD) 18 to the distal end portion of the scintillator14 of the completed scintillator panel 3 such that the light-receivingportion opposes the distal end portion (see FIG. 5).

According to the radiation image sensor 4 of this embodiment, radiationincident from the substrate 10 side is converted into light by thescintillator 14 and detected by the image sensing element 18. In thiscase, since a-C substrate 10 has high radiation transmittance, theamount of radiation absorbed by the substrate 10 can be reduced. Hence,the amount of radiation reaching the scintillator 14 can be increased.In addition, since the Al film 12 as a reflecting film and the LiF film22 as a low-refractive-index member are formed, light incident on thelight-receiving portion of the image sensing element 18 can beincreased. This makes it possible to sharpen the image detected by theradiation image sensor.

As shown in FIG. 10, if the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 40 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 4 is 300%. If the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 50 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 4 is 270%. If the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 60 kv asa tube voltage to the half-wave rectifying x-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 4 is 260%.

The third embodiment of the present invention will be described next.Note that the same reference numerals denoting the parts of thescintillator panels 1 and 3 and radiation image sensors 2 and 4 as inthe first and second embodiments denote the same parts in the thirdembodiment.

FIG. 6 is a sectional view of a scintillator panel 5. FIG. 7 is asectional view of a radiation image sensor 6. As shown in FIG. 6, thesurfaces of a-C substrate 10 of the scintillator panel 3 have undergonesandblasting, and an LiF film (thin transparent film) 22 is formed onone surface. A columnar scintillator 14 for converting incidentradiation into visible light is formed on the surface of the LiF film22. Note that Tl-doped CsI is used for the scintillator 14. Thescintillator 14 is covered with a polyparaxylylene film 16, togetherwith the substrate 10.

As shown in FIG. 7, the radiation image sensor 6 has a structure inwhich an image sensing element 18 is stuck to the distal end portionside of the scintillator 14 of the scintillator panel 5.

The steps in manufacturing the scintillator panel 5 will be describednext. First of all, sandblasting is performed on the surfaces of therectangular or circular a-C substrate 10 (thickness: 1 mm) by usingglass beads (#800), thereby forming fine projections/recesses on thesurfaces of the substrate 10.

The LiF film 22 as a low-refractive-index member is then formed on onesurface of the substrate 10 to a thickness of 100 nm by vacuum vapordeposition. A Tl-doped columnar CsI crystal is grown on the surface ofthe LiF film 22 by vapor deposition to form the scintillator 14 having athickness of 250 μm. The polyparaxylylene film 16 is formed to athickness of 10 μm by the CVD method. With this process, thepolyparaxylylene film 16 is formed on the entire surfaces of thescintillator 14 and substrate 10. Since the polyparaxylylene film 16 isformed on the surfaces of the substrate 10, the moisture-proofcharacteristics of the scintillator 14 can be improved. In addition,since the polyparaxylylene film 16 is formed on the entire surfaces ofthe substrate 10, the moisture-proof characteristics of the scintillator14 can be further improved.

The radiation image sensor 6 is manufactured by sticking the imagesensing element (CCD) 18 to the distal end portion side of thescintillator 14 of the completed scintillator panel 5 such that thelight-receiving portion opposes the distal end portion side (see FIG.7).

According to the radiation image sensor 6 of this embodiment, radiationincident from the substrate 10 side is converted into light by thescintillator 14 and detected by the image sensing element 18. In thiscase, since a-C substrate 10 has high radiation transmittance, theamount of radiation absorbed by the substrate 10 can be reduced. Hence,the amount of radiation reaching the scintillator 14 can be increased.In addition, since the LiF film 22 is formed as a low-refractive-indexmember, light satisfying the total reflection condition is reflected bythe interface between the scintillator 14 and the LiF film 22, and theamount of light incident on the light-receiving portion of the imagesensing element 18 can be increased. This makes it possible to sharpenthe image detected by the radiation image sensor.

As shown in FIG. 10, if the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 40 kv asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 6 is 220%. If the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 50 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 6 is 200%. If the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 60 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 6 is 190%.

The fourth embodiment of the present invention will be described next.Note that the same reference numerals denoting the parts of thescintillator panel 1 and radiation image sensor 2 as in the firstembodiment denote the same parts in the fourth embodiment.

FIG. 8 is a sectional view of a scintillator panel 7. FIG. 9 is asectional view of a radiation image sensor 8. As shown in FIG. 8, onesurface and side surfaces of a-C substrate 10 of the scintillator panel7 have undergone sandblasting, and the other surface is mirror-polished.

A columnar scintillator 14 for converting incident radiation intovisible light is formed on the other surface of this substrate. Notethat Tl-doped CsI is used for the scintillator 14. The scintillator 14is covered with a polyparaxylylene film 16, together with the substrate10.

As shown in FIG. 9, the radiation image sensor 8 has a structure inwhich an image sensing element 18 is stuck to the scintillator 14 sideof the scintillator panel 7.

The steps in manufacturing the scintillator panel 7 will be describednext. First of all, sandblasting is performed on the surfaces of therectangular or circular a-C substrate 10 (thickness: 1 mm) by usingglass beads (#800), thereby forming fine projections/recesses on thesurfaces of the substrate 10. In addition, the other surface of thesubstrate 10 is mirror-polished.

A Tl-doped columnar CsI crystal is grown on the other surface of thesubstrate 10 by vapor deposition to form the scintillator 14 having athickness of 250 μm. The polyparaxylylene film 16 is formed to athickness of 10 μm by the CVD method. With this process, thepolyparaxylylene film 16 is formed on the entire surfaces of thescintillator 14 and substrate 10. Since the polyparaxylylene film 16 isformed on the surfaces of the substrate 10, the moisture-proofcharacteristics of the scintillator 14 can be improved. In addition,since the polyparaxylylene film 16 is formed on the entire surfaces ofthe substrate 10, the moisture-proof characteristics of the scintillator14 can be further improved.

The radiation image sensor 8 is manufactured by sticking the imagesensing element (CCD) 18 to the distal end portion side of thescintillator 14 of the completed scintillator panel 7 such that thelight-receiving portion opposes the distal end portion side (see FIG.9).

According to the radiation image sensor 8 of this embodiment, radiationincident from the substrate 10 side is converted into light by thescintillator 14 and detected by the image sensing element 18. In thiscase, since a-C substrate 10 has high radiation transmittance, theamount of radiation absorbed by the substrate 10 can be reduced. Hence,the amount of radiation reaching the scintillator 14 can be increased.This can increase the amount of light incident on the light-receivingportion of the image sensing element 18, thereby sharpening the imagedetected by the radiation image sensor 8.

As shown in FIG. 10, if the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 40 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 8 is 150%. If the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 50 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 8 is 135%. If the output obtained when the conventionalradiation image sensor detects the X-ray generated by applying 60 kV asa tube voltage to the half-wave rectifying X-ray tube is assumed to be100%, the output obtained when the X-ray is detected by the radiationimage sensor 8 is 130%.

In each embodiment described above, the polyparaxylylene film 16 isformed on the entire surfaces of the substrate 10. However, thepolyparaxylylene film 16 may be formed on a part of the surfaces of thesubstrate 10. For example, the polyparaxylylene film 16 may be formed ona part of the exposed surface of the substrate 10, having noscintillator thereon.

In each embodiment described above, the a-C substrate is used. However,a graphite substrate may be used. The graphite substrate has highradiation transmittance like the a-C substrate. In this case, therefore,the amount of radiation reaching the scintillator can be increased as inthe case wherein the a-C substrate is used.

In the above embodiments, a LiF film is used as a thin transparent film.However, a film made of a material containing selected from the groupconsisting of LiF, MgF₂, CaF₂, SiO₂, Al₂O₃, MgO, NaCl, KBr, KCl, andAgCl may be used.

In each embodiment described above, CsI (Ti) is used as the scintillator14. However, the present invention is not limited to this. For example,CsI (Na), NaI (Tl), LiI (Eu), or KI (Tl) may be used.

In each embodiment described above, examples of the polyparaxylylene arepolymonochloroparaxylylene, polydichloroparaxylylene,polytetrachloroparaxylylene, polyfluoroparaxylylene,polydimethylparaxylylene, and polydiethylparaxylylene.

According to the scintillator panel of the present invention, since thesubstrate made of carbon as a major constituent has high radiationtransmittance, the amount of radiation absorbed by the substrate can bedecreased, and the amount of radiation reaching the scintillator can beincreased.

In addition, according to the radiation image sensor of the presentinvention, since the scintillator panel has the substrate made of carbonas a major constituent having high radiation transmittance, the amountof light reaching the image sensing element can be increased.

As described above, the scintillator panel and radiation image sensor ofthe present invention are suited for medical X-ray photography and thelike.

1. A radiation image sensor comprising: a scintillator pane, wherein the scintillator panel comprises: a radiation transmittable substrate; a scintillator facing toward on a radiation emitting surface of said substrate; and a protective film, which transmits light generated by said scintillator, substantially encapsulating said substrate and said scintillator, wherein said protective film is an organic film substantially continuously formed on upper and side surfaces of said scintillator and substrate as a single integral component; and an image sensing element facing toward and optically coupled with said scintillator.
 2. A radiation image sensor according to claim 1, further comprising a reflecting film formed between said substrate and said scintillator.
 3. A radiation image sensor according to claim 1, wherein said scintillator is a columnar scintillator comprising multiple scintillator columns.
 4. A scintillator panel comprising: a radiation transmittable substrate; a scintillator deposited on a radiation emitting surface of said substrate; and a protective film, which transmits light generated by said scintillator, substantially encapsulating said substrate and said scintillator, wherein said protective film is an organic film substantially continuously formed on upper and side surfaces of said scintillator and substrate as a single integral component.
 5. A scintillator panel according to claim 4, further comprising a reflecting film formed between said substrate and said scintillator.
 6. A scintillator panel according to claim 4, wherein said scintillator is a columnar scintillator comprising multiple scintillator columns. 